This document defines key terms in algebra: a variable represents an unknown number, an algebraic expression combines numbers, variables and operations, and evaluating an expression means substituting values for variables. It provides examples of writing algebraic expressions from word phrases describing addition and subtraction situations. Finally, it has examples of evaluating and completing tables with algebraic expressions.

1. Algebra I

2. Definitions

Variable – A variable is a letter
or symbol that represents a
number (unknown quantity).

8 + n = 12

3. Definitions

A variable can use any letter of
the alphabet.

n+5

x–7

w - 25

4. Definitions

Algebraic expression – a group of
numbers, symbols, and variables
that express an operation or a
series of operations.

m+8

r–3

5. Definitions

Evaluate an algebraic expression –
To find the value of an algebraic
expression by substituting
numbers for variables.

m+8 m = 2 2 + 8 = 10

r–3 r=5 5–3=2

6. Definitions

Simplify – Combine like terms
and complete all operations
m=2

m+8+m 2m+8

(2 x 2) + 8 4 + 8 = 12

7. Words That Lead to Addition

Sum

More than

Increased

Plus

Altogether

8. Words That Lead to
Subtraction

Decreased

Less

Difference

Minus

How many more

9. Write Algebraic Expressions
for These Word Phrases

Ten more than a number n + 10

A number decrease by 5 w-5

6 less than a number x-6

A number increased by 8 n+8

The sum of a number & n+9
9 y+4

10. Write Algebraic Expressions
for These Word Phrases

A number s plus 2 s+2

A number decrease by 1 k-1

31 less than a number x - 31

A number b increased by b+7
7 n+6

The sum of a number & 6 z+9

11. Evaluate each algebraic expression when
x = 10

x+8 18

x + 49 59

x+x 20

x-x 0

x-7 3

42 - x 32

12. Complete This Table
n n-3
5 2
10 7
21 18
32 29

13. Complete This Table
x x+6
11
16
27
21 38

14. Write an Algebraic Expression for These
Situations

Scott’s brother is 2 years younger than
Scott
s-2

The sum of two numbers is 12
v + c = 12

The difference between two numbers is 5
m–n=5